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Mechanistic Insights into Phenol Oxidation by a Copper(II) Complex of a Pyridine‐ and Amide‐Containing Copolymer in an Aqueous Medium
Author(s) -
Lykourinou Vasiliki,
Ming LiJune
Publication year - 2015
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201402778
Subject(s) - chemistry , aqueous solution , hydroxylation , phenol , autoxidation , pyridine , amide , copper , medicinal chemistry , organic chemistry , polymer chemistry , enzyme
A Cu II complex of a pyridine‐ and amide‐containing copolymer (Cu‐ P1 ) exhibits effective activity toward phenol hydroxylation in 50 % aqueous methanol solution at apparent pH 8.0 and 25 °C. The complex shows significant first‐order rate accelerations of 4.2 × 10 5 and 1.4 × 10 5 relative to phenol autoxidation in air and in the presence of 20 m M H 2 O 2 , respectively. The reaction mechanisms with H 2 O 2 and air are different on the basis of (a) the different activity profiles for Cu binding, (b) the different deuterium kinetic isotope effects (2.8 in 20 m M H 2 O 2 and 1.2 aerobically), and (c) the formation of a dinuclear substrate–(Cu‐ P1 ) complex with H 2 O 2 but a mononuclear one aerobically. The mechanism in the presence of H 2 O 2 is consistent with that of the type‐3 dicopper tyrosinase. Although oxidized di‐Cu II tyrosinase can only use H 2 O 2 for phenol hydroxylation, Cu II ‐ P1 can use either air or H 2 O 2 for this process. The studies herein introduce a versatile chemical system for the further exploration of Cu–oxygen chemistry and other types of metal‐centered chemistry and for the aerobic degradation of aromatic compounds in environmental and green chemistry.